![]() However, there is now general agreement that chimpanzees also use tools, in captivity ( Kohler, 1927) as well as in the wild ( Beck, 1980 Whiten et al., 1999). Tool use has long been considered a uniquely human characteristic ( Oakley, 1956), dating back 2.5 Mi years ( Ambrose, 2001). Tools are mechanical implements that allow individuals to achieve goals that otherwise would be difficult or impossible to reach. These results shed new light on the changes of the hominid brain during evolution. In conclusion, while the observation of a grasping hand activated similar regions in humans and monkeys, an additional specific sector of IPL devoted to tool use has evolved in Homo sapiens, although tool-specific neurons might reside in the monkey grasping regions. This latter site was considered human-specific, as it was not observed in monkey IPL for any of the tool videos presented, even after monkeys had become proficient in using a rake or pliers through extensive training. In humans, the observation of actions done with simple tools yielded an additional, specific activation of a rostral sector of the left inferior parietal lobule (IPL). In both species, the observation of an action, regardless of how performed, activated occipitotemporal, intraparietal, and ventral premotor cortex, bilaterally. In a comparative fMRI study, we scanned a large cohort of human volunteers and untrained monkeys, as well as two monkeys trained to use tools, while they observed hand actions and actions performed using simple tools. It does not store any personal data.Though other species of primates also use tools, humans appear unique in their capacity to understand the causal relationship between tools and the result of their use. The cookie is set by the GDPR Cookie Consent plugin and is used to store whether or not user has consented to the use of cookies. The cookie is used to store the user consent for the cookies in the category "Performance". This cookie is set by GDPR Cookie Consent plugin. ![]() The cookie is used to store the user consent for the cookies in the category "Other. The cookies is used to store the user consent for the cookies in the category "Necessary". The cookie is set by GDPR cookie consent to record the user consent for the cookies in the category "Functional". The cookie is used to store the user consent for the cookies in the category "Analytics". These cookies ensure basic functionalities and security features of the website, anonymously. Necessary cookies are absolutely essential for the website to function properly. The findings of the study also challenge the assumption that a chimp-like hand was the starting point of the chimpanzee-human LCA. These results support the hypothesis that the long thumb to fingers ratio of the human hand was acquired convergently with other highly dexterous anthropoids. Their results show the more recent, convergent evolution of finger elongation in chimpanzees and orangutans and comparatively little change between humans, human ancestors and gorillas. The researchers measured the hand proportions of humans, living and fossil apes as well as fossils of human ancestors including Ardipithecus ramidus and Australopithecus sediba, to understand the step wise evolution of the hand. This is one of the most distinctive traits of humankind compared to apes and is often cited as one of the reasons for the success of the species however there are competing theories on how the human hand evolved over time. Human hands exhibit a long thumb in relation to the fingers. These findings indicate that the structure of the modern human hand is largely primitive in nature, rather than the result of selective pressures in the context of stone tool-making. Human hand proportions have changed little from those of the last common ancestor (LCA) of chimpanzees and humans. The work is done by Stony Brook University’s Sergio Almecija, Jeroen Smaers and William Jungers. Two days ago, Nature published a paper “The evolution of human and ape hand proportions,”a study that discovers that human hands may be more primitive than chimp’s. ![]() A study about the evolution of the human shows there has been relatively little change in its proportions.
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